Non-classical correlations between a C-band telecom photon and a stored spin-wave

TL;DR

This paper demonstrates non-classical correlations between a telecom wavelength photon and a stored spin-wave in an atomic ensemble, a key step for quantum networks and repeaters over long distances.

Contribution

It reports the first demonstration of non-classical correlation between a telecom photon and a stored spin-wave using frequency conversion in an integrated device.

Findings

Achieved high signal-to-noise ratio in photon conversion

Demonstrated quantum correlation between telecom photon and spin-wave

Enabled potential for long-distance quantum communication

Abstract

Future ground-based quantum information networks will likely use single photons transmitted through optical fibers to entangle individual network nodes. To extend communication distances and overcome limitations due to photon absorption in fibers the concept of quantum repeaters has been proposed. For that purpose, it is required to achieve quantum correlations between the material nodes and photons at telecom wavelengths which can be sent over long distances in optical fibers. Here we demonstrate non-classical correlation between a frequency converted telecom C-band photon and a spin-wave stored in an atomic ensemble quantum memory. The photons emitted from the ensemble and heralding the spin-waves are converted from 780 nm to 1552 nm by means of an all-solid-state integrated waveguide non-linear device. We show ultra-low noise operation of the device enabling a high signal to noise ratio of the converted single photon, leading to a high spin-wave heralding efficiency. The presented work is an enabling step towards the practical entanglement of remote quantum memories and the entanglement of quantum systems operating at different wavelengths.